With the aging of the American workforce, the largest percentage increase in employment is occurring in the 55-64 year old age group. This research is designed to assess effects of workplace biomechanical, psychosocial, organizational and non-workplace factors on normal age related changes in musculoskeletal function and performance. There are particular emphases on the role of gender and on identifying sub- populations that may be at increased risk of exceeding age expected changes in musculoskeletal function and performance. We use the term musculoskeletal health (MSH) to define the complex of physiological performance and effective function. An estimated 1200-1400 workers representing both genders, and meeting a broad age demographic, will be studied in Connecticut manufacturing facilities. Their evaluation will include questionnaires that survey individual, organizational and psychosocial factors; direct measures of physical performance, strength and muscle power; and instrumented and observed exposure measurement. There are cross-sectional and longitudinal components employed in a mixed design that accommodates the relatively short study period, and the longer time span of many health outcomes relevant to the musculoskeletal system. A key aspect of this study is the influence of the so-called healthy worker survivor effect, the extent to which musculoskeletal symptoms and function influence withdrawal from the workforce. This is addressed through several imputative models. We will also estimate the interactive effect of risk factors (extrinsic and intrinsic) on the distribution of subjective and objective findings and undertake the compilation of broader indices of MSH.